1. Field of the Invention
The present invention relates to tubing/casing annulus plug additives and to methods of making such additives, to tubing/casing annulus plug treatment fluids made therefrom and to methods of making such fluids, to methods of modifying a well fluid using such additives and/or fluids, to methods of operating a well using such additives and/or fluids, and to methods of plugging a tubing/casing annulus in a well bore. In another aspect, the present invention relates to tubing/casing annulus plug additives comprising polymer, crosslinking agent, filter aid, and optionally reinforcing materials and to methods of making such additives, to tubing/casing annulus plug treatment fluids made therefrom and to methods of making such fluids, to methods of modifying a well fluid using such additives and/or fluids, to methods of operating a well using such additives and/or fluids, and to methods of plugging a tubing/casing annulus in a well bore. In another aspect, the present invention relates to tubing/casing annulus plug additives comprising a dry mixture of polymer, crosslinking agent, filter aid, and optionally reinforcing materials and to methods of making such additives, to tubing/casing annulus plug treatment fluids made therefrom and to methods of making such fluids, to methods of modifying a well fluid using such additives and/or fluids, to methods of operating a well using such additives and/or fluids, and to methods of plugging a tubing/casing annulus in a well bore. In even another aspect, the present invention relates to additives comprising polymer and diatomaceous earth (“DE”) and to methods of making such additives, to tubing/casing annulus plug treatment fluids made therefrom and to methods of making such fluids, to methods of modifying a well fluid using such additives and/or fluids, to methods of operating a well using such additives and/or fluids, and to methods of plugging a tubing/casing annulus in a well bore.
2. Description of the Related Art
Portland cement is commonly used in oil field applications such as oil well cement jobs. Portland cements can be tailor-made for the specific conditions of each well. A description of the state of the art in oil well cementing technology is given in Basic Cementing, Petroleum Publishing Co., 1977 (reprinted from a series of articles appearing in the Oil and Gas Journal) and Rike, J. L., et al, Squeeze Cementing: State of The Art, Journal of Petroleum Technology, (January 1982), pp. 37-45.
Formulation of the cement in the field is largely a product of trial and error by field personnel to meet irregularities in the cementing composition and the downhole environment. Cement quality control is difficult to achieve under such conditions. As a result, Portland cement can exhibit premature set-up, cracking, or shrinking upon curing. This feature of Portland cement limits its usefulness in wellbore treatments to repair leaks in wellbore casing or tubing by plugging the tubing/casing pair annulus. Use of other available methods to remedy leaking wellbore tubulars, including workovers and redrilling, can be extremely cumbersome and expensive.
U.S. Pat. No. 4,730,674, issued Mar. 15, 1988 to Burdge et al., noted that a wellbore treatment process was needed for preventing or repairing leaking tubulars which was both economically and operationally attractive. Burdge et al. further noted that a process was needed which effectively employed a plugging material having a broad range of highly controllable and predictable set-up times for ease of operation and design. Burdge et al. even further noted that a process was needed which employed a plugging material which was not as susceptible as Portland cement to shrinking and cracking when applied to a tubing/casing annulus in a wellbore.
In an effort to overcome the deficiencies of the prior art and to fulfill the perceived needs, U.S. Pat. No. 4,730,674 discloses the use of a water soluble carboxylate crosslinking polymer along with a chromic carboxylate complex crosslinking agent in the plugging of a tubing/casing annulus in a wellbore, and at column 2, lines 30-35, specifically teaches away from the use of solids in the plugging fluid injected into the wellbore.
Thus, while U.S. Pat. No. 5,377,760, issued Jan. 3, 1995 to Merrill discloses addition of fibers to an aqueous solution of partially hydrolyzed polyacrylamide polymer, with subsequent injection into the subterranean to improve conformance, the performance requirements of conformance improvement treatment polymers are so different from those of polymers for plugging an abandoned well, that such would not necessarily work for plugging tubing/casing annulus. Furthermore, Burdge et al. teach away from injection a solid containing polymer into the wellbore to plug a tubing/casing annulus.
Additionally, Merrill's conformance treatment method of mixing the fibers with the polymer solution followed by injection, requires a multiplicity of storage and mixing tanks, and a metering system which must be operated during the operation of the well. Specifically, a first tank will store a water and polymer solution, a second tank will store a water and cross-linking solution, and a third tank will be used to mix fibers with polymer solution from the first tank to create a polymer/fiber slurry. This polymer/fiber slurry is then metered from the third tank and combined with crosslinking solution metered from the second tank to the well bore.
As an advance over the above prior art, U.S. Pat. No. 6,218,343, issued Apr. 17, 2001, to Boyce D. Burts, Jr., for “Additive for, treatment fluid for, and method of plugging a tubing/casing annulus in a well bore,” discloses an additive including a dry mixture of water soluble crosslinkable polymer, a crosslinking agent, and a reinforcing material of fibers and/or comminuted plant materials. The method of forming a fluid includes contacting the additive with water or an aqueous solution, with a method of treating the formation further including the step of injecting the fluid into the formation.
While not believed to be related prior art because they relate to different types of well operations, for completeness, attention is directed to five other similar “dry mixture” patents by Boyce D. Burts, Jr., which were filed on the same day (Oct. 31, 1997) as the '343 Patent: U.S. Pat. No. 6,102,121, issued Aug. 15, 2000, for “Conformance improvement additive, conformance treatment fluid made therefrom, method of improving conformance in a subterranean formation,” U.S. Pat. No. 6,098,712, issued Aug. 8, 2000, for “Method of plugging a well,” U.S. Pat. No. 6,016,879, issued Jan. 25, 2000, for “Lost circulation additive, lost circulation treatment fluid made therefrom, and method of minimizing lost circulation in a subterranean formation,” U.S. Pat. No. 6,016,871, issued Jan. 25, 2000, for “Hydraulic fracturing additive, hydraulic fracturing treatment fluid made therefrom, and method of hydraulically fracturing a subterranean formation,” and U.S. Pat. No. 6,016,869, issued Jan. 25, 2000, for “Well kill additive, well kill treatment fluid made therefrom, and method of killing a well.”
A number of patents discuss the use of diatomaceous earth (“DE”) in a well operation.
U.S. Pat. No. 3,380,542, issued Apr. 30, 1968 to Clear, for restoring lost circulation discloses a oil-based drilling fluid, containing a slurry of diatomite and asbestos, used to restore lost circulation during well drilling operations.
U.S. Pat. No. 4,369,844, issued Jan. 25, 1983 to Clear, discloses that various formation sealing agents have been used in the art to form formation seals and/or filter cakes on the wall of a well bore, including diatomaceous earth.
U.S. Pat. No. 4,110,225, issued Aug. 29, 1978 to Cagle, discloses that zones of lost circulation and other undesired fluid communication channels into a wellbore are sealed by isolating a volume in the well including such a zone and applying greater than formation pressure to a novel slurry spotted in the zone until it hardens into a solid, drillable seal. The slurry contains per barrel from 5-50 pounds diatomaceous mix, from about 35 to about 350 pounds of oil well cement, and at a minimum about 5 to 6 pounds of a flake type lost-circulation agent. This '225 patent cites a number of patents that disclose cement/diatomaceous earth compositions, including U.S. Pat. Nos. 2,585,336; 2,793,957; 2,961,044; 3,467,198; and 3,558,335.
Regarding these patents, the '225 patent notes the following:                Regarding U.S. Pat. No. 2,585,336, the '225 patent notes, “a mixture is made using from 2% to 100% diatomaceous earth, compared to the content of the cement in the slurry. The aim of the inventors was to prevent perlite from settling and to produce a lightweight cement. The diatomaceous earth-cement described in the disclosure is a mixture of Portland cement, perlite and diatomaceous earth, lime, and asbestos fibers.”        Regarding U.S. Pat. No. 2,793,957, the '225 patent notes, “refers to a highly permeable cement formed by use of the same basic mixtures of diatomaceous earth with Portland cement, the diatomaceous earth present being from five to seven times the proportion of the Portland cement in the slurry. The aim of the inventors was to produce a light highly permeable cement, entirely opposite to the purpose of my invention.”        Regarding U.S. Pat. No. 2,961,044, the '225 patent notes, “discusses and claims a cement composition which has diatomaceous earth in the amounts of from 30% to 70% of the Portland cement. The reason for using the diatomaceous earth was to prevent the strength retrogression of a salt-saturated cement. Thus, while Shell wishes (among other uses) to employ his mixture for squeeze cementing, he produces a relatively high-strength cement plug. There is a real tendency when redrilling such a plug for the bit to be deflected or sidetracked so that the new hole is beside rather than through the bore and the seal is ineffective. This is completely different from my invention which minimizes such tendency by producing a plug at least as drillable as the formation in which it is set. Also, Shell is directed to operations using salt-saturated cement slurries, while I prefer using a fresh or brackish water slurry. I employ lost-circulation agents; he makes no teaching of using such additives. Accordingly, his teaching is quite far from mine.”        Regarding both U.S. Pat. Nos. 3,467,198 and 3,558,335, the '225 patent notes, “describe cement compositions having diatomaceous mix present in the amounts from 0.5% to 10% of the amount of Portland cement present to prevent solids-settling.”        
U.S. Pat. No. 4,369,844, issued Jan. 25, 1983 to Clear, discloses slurries to seal permeable earth formations encountered in the drilling of wells, comprising finely divided paper, diatomaceous earth, and in a further embodiment, lime. A slug of the slurry is spotted at the locus of the permeable formation and defluidized to form a formation seal on which a mud sheath is then deposited.
U.S. Pat. No. 4,505,751, issued Mar. 19, 1985, discloses a silicate/silica cement in oil field applications, including diatomaceous earth as a species of silica compound.
While not believed to be analogous prior art because it relates to earthen pits (for example a ditch) and not to subterrean wellbores nor well operations, U.S. Pat. No. 5,947,644, issued Sep. 7, 1999 to Gibbons et al., is included herein for completeness because it discloses a gelable slurry of aqueous solvent, a crosslinkable polymer, a crosslinking agent, and unconsolidated solids such as diatomaceous earth. This gelable slurry is placed in an earthen pit and allowed to form into a fluid impermeable barrier wall in the earthen pit. The polymer serves to bind the unconsolidated solids to convert the gelable slurry to a non-deformable gelled continuum of consolidated solids, which forms the barrier wall in the earthen pit. As disclosed in the '644 patent in the Summary of the Invention section, at col. 1, lines 57-67, this gelable slurry is prepared by first forming a liquid gelation solution of the polymer and crosslinking agent, to which is subsequently mixed with the unconsolidated solids, or alternatively, by sequentially mixing the aqueous solvent, crosslinkable polymer, and polymer crosslinking agent with the unconsolidated solids.
Thus, in spite of the advancements in the prior art, there still need for further innovation in the tubing/casing annulus plug additives.
There is need for further innovation for tubing/casing annulus plug additives utilizing a water soluble polymer.
There is another need for a tubing/casing annulus plug additive which would allow for simplification of the mixing equipment.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.